Details of their association emerged as Robinson was granted bail on a charge of murdering the 52-year-old warder in March.

Mr Ismay suffered serious leg injuries when a booby-trap device exploded under a van he was driving in east Belfast.

He had been recovering, but died after being returned to hospital 11 days later.

Dissident republican group the New IRA has claimed responsibility for the attack.

Robinson, of Aspen Park in the Dunmurry area of the city, is also charged with possessing explosives with intent to endanger life.

Prosecutors claim he is linked to the bombing by CCTV footage of a car believed to have been used to plant the device at the victim's Hillsborough Drive home early on March 4.

It was claimed that Robinson borrowed and then drove the Citroen vehicle to the scene.

A Crown lawyer said forensic examination of the car confirmed traces of RDX, an identifier in high explosive material, on its rear floor and seats.

Cell-site analysis of alleged phone calls between Robinson and the vehicle's owner also features in the case.

The prosecution barrister said: "During the course of interviews the applicant accepted he knew the deceased, the two of them had worked on voluntary emergency transport units with the St John's Ambulance team.

"He said they had a good working relationship with one another."

Opposing bail, he argued there is a risk of further bomb attacks against prison officers, members of the PSNI and "anyone seen as a target for dissident republican activity".

Mr Justice Colton also heard attempts could be made to interfere with a civilian witness.

"This is a case in which the deceased died tragically 11 days after the event... he was released home and died of a blood clot," the barrister said.

"There's going to be all sort of complications about causation."

Mr Devine also stressed his client will be so closely monitored that there is no chance of involvement with organisations relying on "clandestine behaviour and secrecy".

He revealed that the accused, formerly a social worker, had been training to become a paramedic.

Acknowledging the "natural revulsion" at the allegations, the judge added: "I note the applicant in this case knew the victim and claims he got on quite well with him which, if if he is in fact guilty of the offence, makes it all the more heinous."

But granting bail, Mr Justice Colton held that Robinson was now well-known to the authorities, diminishing the risk of any re-offending.

He ordered the accused to abide by a curfew, electronic monitoring and report to police every day.

Robinson is also banned from contacting a witness in the case, entering part of east Belfast or travelling in a private car.